Muhamad Awang

Air quality in Malaysia: impacts, management issues and future challenges.

Observations have been made on the long‐term trends of major air pollutants in Malaysia including nitrogen dioxide, carbon monoxide, the ozone and total suspended particulate matter (particularly PM10), and sulfur dioxide, emitted from industrial and urban areas from early 1970s until late 1998.

Light reduction by regional haze and its effect on simulated leaf photosynthesis in a tropical forest of Malaysia

The general level of haze has increased rapidly in tropical regions over the last decades. To reveal the effects of haze on tropical forest ecosystem, photosynthetic photon flux density (PFD) at the top of and within a tropical forest canopy was measured on days with and without visible haze, in the Pasoh Forest Reserve, Peninsular Malaysia. Total daily PFD at 40 m aboveground on hazy days was only about 50% of that on the days without visible haze. The reduction of PFD on hazy days was much larger at 50 cm aboveground within the forest. During the period with haze, the forest understory received few PFD higher than 50 μ mol photons m−2 s−1. Photosynthetic carbon gain was estimated to examine the potential effect of PFD extinction by haze. Under hazy conditions, the simulated net carbon gain, which included photosynthetic carbon gain of daytime and respiratory carbon loss at night, decreased to about −6 mmol CO2 m−2 for an ‘average’ shade leaf of understory plants. This marked decrease of leaf carbon gain might have important impacts on the growth and survival of understory plants, and therefore on the regeneration of tree species in the tropical forest.

Ontogenetic changes in leaf phenology of a canopy species, Elateriospermum tapos (Euphorbiaceae), in a Malaysian rain forest

Leaf phenology was studied in individuals of a canopy species, Elater- iospermum tapos (Euphorbiaceae), at various ontogenetic stages, in a Malaysian rain forest. The timing of leaf emergence was not synchronized among sapling indi- viduals, and was not correlated with any meteorological factors of the preceding month. The timing of leaf fall in saplings was positively correlated with net radi- ation, and maximum and minimum temperature, but negatively correlated with relative humidity the preceding month, although these correlations were weak. The leaf production rate was larger under higher light, but the leaf fall rate was not related to the light regime of the saplings. Thus, leaf production was enhanced by the light availability for each individual, while leaf fall may have been enhanced by drought stress. Non-synchronous leaf production appears to be important for sapling growth, allowing saplings to occupy better-lit space quickly. On the other hand, tall trees showed a clear synchronous leaf-fall pattern, with an annual cycle, and no meteorological factors were correlated with the timing of leaf fall. Mature trees of this species produced flowers simultaneously with new leaves, after shed- ding their leaves. This suggests that the need to synchronize flowering might be the primary determinant of leaf production phenology in mature individuals.

Midday depression of photosynthesis in Enkleia malaccensis, a woody climber in a tropical rainforest

We measured the diurnal changes in net photosynthetic rate (PN) and stomatal conductance (gs) of the leaves of a liana, Enkleia malaccensis Griff. (Thymelaeaceae), at the canopy level in the lowland tropical rainforest at Pasoh, Peninsular Malaysia. The measurements were made from a canopy walkway system, 30 m from the ground for 3 d in March 2003. PN increased with increasing photosynthetically active radiation (PAR) before noon, though PN was not enhanced by the strong radiation hit in the afternoon. Plotting gs at saturating PAR (>0.5 mmol m−2 s−1) against the vapour pressure deficit (VPD) failed to reveal a significant correlation between VPD and gs, and gs became very low at VPD >2.5 kPa. The relationship between PN and gs was fitted on the same regression line irrespective of measuring day, indicating that this relationship was not influenced by either VPD or leaf temperature (TL). Therefore, in the liana E. malaccensis, an increase in VPD leads to partial stomatal closure and, subsequently, reductions in PN and the midday depression of PN of this plant.

Fruit dispersal of two dipterocarp species in a Malaysian rain forest

Seed dispersal is the predominant mobile stage for sessile plants, and critically affects the distribution patterns of the species (Nathan & Muller-Landau 2000). Thus, seed dispersal patterns are important in understanding the population dynamics of the species. Tropical rain forests of Southeast Asia are characterized by the dominance of the family Dipterocarpaceae. Most dipterocarp species reach the emergent layer of the forest, about 40-60 m in height (Whitmore 1984). The fruits have two to five long wings (elongated sepals) and are dispersed by wind. The fruits germinate without dormancy (Whitmore 1984). Therefore, the distance of primary dispersal by wind is critical for the distribution of most dipterocarp species (Suzuki & Ashton 1996). Wind speed is much higher in the emergent layer than in the canopy and understorey layers in a tropical rain forest (Aoki et al. 1978), and winddispersed tree species are especially abundant in the former (Suzuki & Ashton 1996). This suggests that wind speed and height strongly influence the fruit dispersal of wind-dispersed species. In addition, differences in fruit size

The application of an life cycle inventory (LCI) model for solid waste disposal systems in malaysia

This paper discusses the application of an LCt model for solid waste management systems in Malaysia. The model was used to analyze the environmental and economic impacts of municipal waste management systems in Malaysia. In the first part of the study, the LCI model was adapted to analyze waste management systems of four selected cities: Kuala Lumpur and Penang to represent urban areas; Seremban to represent moderately urban areas and Muar to represent rural areas. The results have shown that Kuala Lumpur and Penang had greater Global Warming Potential (GWP) and the costs spent on the solid waste management were also higher as compared to that in suburban areas. In the second part of the study, a detailed evaluation was carried out by analyzing the implication of introducing incineration and composting into the solid waste management system, and the results were compared with the current system, i.e. 100 % landfilled. The relative GWP was lower for incineration, but the cost was extremely high. The results also showed that the final solid waste to be disposed to landfills and the impact due to water emissions could be reduced significantly when incineration and composting were introduced.

Challenges of global environmental issues on ecosystem management in Malaysia

Environmental problems and their management, particularly when related to urban ecosystems, are becoming increasingly challenging. The end-of-pipe method which has been practiced in the past, and is manifested in our laws and regulations, has gradually changed towards a more pro-active approach. Industries now recognize that environmental management and pollution control are no longer liabilities, but rather opportunities to increase their competitiveness. The general public is increasingly aware of the fact that they have to pay more for management of the environment that is based on the end-of-pipe approach. International agencies and industries world-wide are responding positively with a new paradigm shift towards proactive environmental management through voluntary initiatives. The most challenging task in Malaysia however, is to convince the small and medium scale enterprises to shift from the old to the new management system. While local government agencies remain the key players in the management of urban ecosystems, they still lack human resources and the capacity to handle new challenges. This paper discusses new initiatives towards achieving sustainable urban ecosystem management. It highlights the tools and approaches that are being used as alternatives to the existing end-of-pipe approaches. These tools include, eco-management, wastes minimization, ISO 14000 standardization, design for environment, eco-labeling, life cycle assessment and industrial ecology.

In situ CO2 gas-exchange in fruits of a tropical tree, Durio zibethinus Murray

We examined the in situ CO2 gas-exchange of fruits of a tropical tree, Durio zibethinus Murray, growing in an experimental field station of the Universiti Pertanian Malaysia. Day and night dark respiration rates were exponentially related to air temperature. The temperature dependent dark respiration rate showed a clockwise loop as time progressed from morning to night, and the rate was higher in the daytime than at night. The gross photosynthetic rate was estimated by summing the rates of daytime dark respiration and net photosynthesis. Photosynthetic CO2 refixation, which is defined as the ratio of gross photosynthetic rate to dark respiration rate in the daytime, ranged between 15 and 45%. The photosynthetic CO2 refixation increased rapidly as the temperature increased in the lower range of air temperature Tc (Tc <28.5 °C), while it decreased gradually as the temperature increased in the higher range (Tc ≥28.5 °C). Light dependence of photosynthetic CO2 refixation was approximated by a hyperbolic formula, where light saturation was achieved at 100 μmol m−2 s−1 and the asymptotic CO2 refixation was determined to be 37.4%. The estimated gross photosynthesis and dark respiration per day were 1.15 and 4.90 g CO2 fruit−1, respectively. Thus the CO2 refixation reduced the respiration loss per day by 23%. The effect of fruit size on night respiration rate satisfied a power function, where the exponent was larger than unity.

Morphological and phenological characteristics of leaf development ofDurio zibethinus Murray (Bombacaceae)

The morphological and phenological characteristics of leaf development ofDurio zibethinus Murray were investigated at an experimental field of Universiti Pertanian Malaysia (UPM) in Selangor. Proportionality was observed in the relations of leaf length to leaf width and of leaf area to the product of leaf width and length. The proportionality was explained from the similarity of leaf shape. New leaves emerged continuously, but the number of new leaves fluctuated seasonally. The emergence of leaves was inhibited by the flower bud formation. In the survival curves of leaves, the relative fall rate was lower at the early stage of leaf development than at the late stage. Leaf longevity of 100 to 133 days was low and leaf expansion period of two weeks was short in comparison with the published data on tropical trees. From the ecophysiological viewpoint, the leaf survival strategy of the present species was discussed: the present species manages to set up a photosynthetic system in a short period by the rapid leaf growth; the lower leaf longevity is advantageous to reaching more frequently high photosynthetic production by newly emerged leaves.

Benefits of air quality improvement in Klang Valley Malaysia

The study evaluated the comparative reliability of different question formats of contingent valuation method by resurvey of the same households nine months after their original survey. The test-retest correlations are statistically significant at 1% level. Comparative reliability of different question formats has been tested comparing the test-retest correlations of these methods. This test has revealed that there is no significant difference in the test-retest correlations between the different question formats for either level A (reduction of the concentration of PM10 by 10%) or level B (reduction of the concentration of PM10 by 20%) air quality improvement.